Rifts - World in Chaos

The Rifts World with D20 rules.

Summoning

You can summon elementals, undead, beastial spirits, or planar entities simply by rolling your Arcane Skill check. Each creature added to the summoning after the first adds 5 to the difficulty for small/medium and 10 to the difficulty for Large/Huge. Maximum amount of creatures summoned each spell (called a batch) is your Intellegence Modifier. Summoning a creature/creatures takes one FULLROUND. The Creature/s appear up to 30ft. away from the caster and may attack immediately upon summoning. Stats on the creatures come from 3.5 D&D.

Every time you use a summoning spell, the creatures summoned is considered a “batch”. It takes a swift action to direct the “batch” to move and attack a target. If a batch is not directed within a number of rounds (Int. Mod.) then they sense they are no longer needed and fade back to where they came.